1. Field of the Invention
The present invention generally relates to a software adaptation layer in a telecommunications system, and more particularly to a method an apparatus that permits established legacy software to operate in a new telecommunications system.
2. Background Description
In the telecommunications industry, evolution of products is a continual process. These products are of various specific purposes but relate to switching voice and data communications. Expended investment in development cost and development time for sophisticated telecommunications products has been very large. The equipment that is part of the national and international switching fabric is the result of millions of dollars of design and development investment.
One primary technology that has been the backbone of core telecommunication switching platforms has been Time Division Multiplexing (TDM). TDM has been the preferred internal circuit connection method of central office switches over the last few decades. Extensive hardware interfaces have been designed to provide communication circuitry and supporting feature support. Features such as call waiting, conferencing, tone detection and generation, voice generators, system maintenance, trunk testing, line testing, etc. have been supported by both the hardware design and supporting software (SW) logic controls via microprocessors. The amount of development time and expenditure has been very large.
The supporting software to control the processors within the TDM switching systems has been the result of extensive long-term design efforts involving many hundreds of design engineers over many years. The software within the switching platforms represent extensive industry defined features. These features have been perfected and have reached maturity. As a result, worldwide customers have become familiar with the features and have come to rely upon the proven and consistent behavior. The complexity of the features when considered in view of the total operational requirements of the switching platform represents a proven level of engineering accomplishment which is not easily replicated in time or financial investment.
Technology advances in packet switching has propelled the telecommunications industry into a new era. TDM switching is now being replaced by packet switching concepts also known as soft-switches. Voice and data are now carried routinely in packet switching architectures. The hardware configurations and essence is substantially different in a packet switch. Many functions that were once a hardware implementation in a TDM world is now replaced by software or software with much less discrete hardware components. Much higher capacity microprocessors, digital signal processors, memories, and specialty chips have enabled more features and functions to be done in the software domain.
But the investment of feature capabilities and software design investment in the TDM switching platforms cannot be readily duplicated. Therefore, the extensive software logic programs that was once designed for a TDM switching environment may be leveraged and its actual life extended if a manner of transforming the legacy software into the packet switching domain can be provided.
Migration or reuse of legacy software onto a new packet based switching architecture has several advantageous if the costs or risk is reasonable. If the established base of features and functions within the legacy software can be reused by strategic modifications, the cost and risk of new software designs is substantially mitigated. This technique can result in a familiar and known feature set complement which has demonstrated performance history to become a valuable part of a new packet based communications platform.
A significant subsystem in a TDM legacy telecommunications switch such as a Siemens EWSD (German acronym for Digital Switching System) is a Line and trunk group (LTG) module. The LTG hardware and software control provides the interface between the switching system TDM switching fabric of the coordinating processor and the outside world. The hardware interfaces to the outside world include devices such as T1 trunks, E1 trunks, CCS (common channel signaling) lines, etc. The interface from the LTG to the system coordinating processor (or Network Services Processor) includes two HDLC (High Level Data Link Control) redundant message channels.
The LTG subsystem contains core telecommunications functions such as tone generators, digit receivers, local subscriber TDM cross-connect time switch (connects subscriber A to B or TDM timeslot A to B), and other traditional TDM components such as conference capability and TDM transmission pad level (attenuation) controls.
A given LTG software unit is constrained with a logical sizing limitation. Its inherent design can address and control only 120 trunks and 2048 lines. This legacy design also employed 16-bit software addressing schemes. Migrating a 16-bit software system to 32-bit processor environments is not an easy matter. Interrupts do not work directly, software addressing is limited, and processor advantages are restricted.
The problems to be solved are the conversion and reuse of as much LTG software logic as possible, to keep the established and proven capabilities intact while at the same time expand the effective addressing limits of interface devices, and simultaneously employing more modern software concepts and operating systems.
This software reuse must then operate transparently within the architecture of a packet switching based system The present invention of this application provides a novel solution to these issues.